In tar sands operations, bitumen is generally found in reservoirs comprising high concentrations of saline water. During various stages of processing the bitumen in situ and ex situ, the bitumen and water are prone to forming emulsions comprising water droplets finely dispersed throughout the bitumen matrix. Such emulsions are stabilized by the presence of various surfactant species and fine solids dispersed in the bitumen matrix, including in the aqueous phase, which prevent or interfere with coalescence of the water droplets during processing of bitumen feeds.
The concentration of water and various salt species in the bitumen matrix must be reduced to an acceptable level prior to downstream processing of the bitumen due to equipment operational requirements and the detrimental effects of the salts on the equipment such as corrosion, catalyst poisoning, negative impact on processing efficiencies and cost. Certain hydrocarbon feeds from heavy oil and offshore oil operations may also present similar emulsion and salt content challenges depending on the source of the hydrocarbon feed, and on added water in the hydrocarbon feed which must be subsequently removed for downstream operations.
Various methods have been used in the art to achieve a reduction in the water and salt contents in hydrocarbon feeds. A reduction in both water and salt content in bitumen, for example, may be achieved by removing the water comprising salts, which may include addition of fresh water to the hydrocarbon feed with mixing in order to promote coalescence of the fresh water droplets with saline water droplets, and thereby sediment and remove the saline water. However, in such processes, water-in-oil emulsions generally result from the mixing, and require further processing to promote separation of the hydrocarbon phase from residual water. Examples of conventional separation processes include gravity separation with and without the addition of demulsifiers to break water-in-oil emulsions, centrifugation, and electrostatic field treatment technologies. These processes are, however, often unsuccessful at effectively removing substantially all of the water and salts due to stable micro-emulsion formation.
Therefore, there is a need in the industry for processing hydrocarbon feeds to effect emulsion breaking, desalting, dewatering or a combination thereof to obtain feeds having water and salt contents reduced to levels suitable for downstream processing operations including upgrading.